In the fast-paced world of bedside care, recognizing life-threatening cardiac rhythms quickly can save lives. As a nurse, you don’t need to be a cardiologist, but you must know how to spot these critical arrhythmias on a monitor or EKG strip — and know what to do next.
This guide breaks down the Big 5 — the deadliest heart rhythms every nurse must understand.
❤️ Why These Rhythms Matter
Some arrhythmias can stop the heart from pumping effectively, causing cardiac arrest within seconds or minutes. Knowing them means you can call a code, grab the crash cart, start CPR, and help the team deliver the right treatment without delay.
⚡ The Big 5 Life-Threatening Rhythms
✅ 1. Ventricular Tachycardia (V-Tach)
✅ 2. Ventricular Fibrillation (V-Fib)
✅ 3. Asystole
✅ 4. Pulseless Electrical Activity (PEA)
✅ 5. Torsades de Pointes
Let’s look at each one in plain language.
1️⃣ Ventricular Tachycardia (V-Tach)
What it is:
V-Tach happens when the ventricles fire off fast electrical signals on their own. This overrides the normal pacemaker and can pump blood so poorly that the patient may have no pulse.
What it looks like on EKG:
- Wide, regular QRS complexes.
- Rate often 150–250 bpm.
- Looks like consistent big hills.
Check the patient:
- V-Tach with a pulse: May cause dizziness, hypotension.
- Pulseless V-Tach: Code Blue. Treat like V-Fib.
What to do:
- Stable with pulse: Call the provider, prepare for antiarrhythmic meds (like amiodarone), possible synchronized cardioversion.
- Unstable or pulseless: Start CPR, defibrillate immediately, follow ACLS.
2️⃣ Ventricular Fibrillation (V-Fib)
What it is:
This is total electrical chaos. The ventricles quiver instead of contracting. No blood is pumped — the patient is clinically dead without fast action.
What it looks like on EKG:
- No P waves or QRS complexes.
- Just a squiggly, chaotic baseline.
What to do:
- Call a Code Blue immediately.
- Start CPR.
- Defibrillate ASAP — defibrillation is the only cure.
- Give epinephrine, follow ACLS.
3️⃣ Asystole
What it is:
This is flatline — no electrical activity at all. No heartbeat, no blood flow. True cardiac arrest.
What it looks like on EKG:
- Flat line or nearly flat line (check all leads to be sure it’s not a loose lead).
What to do:
- Call a Code Blue.
- Start CPR immediately.
- Do NOT shock — shocking won’t help because there’s no electrical activity.
- Give epinephrine, try to find reversible causes (like H’s and T’s).
4️⃣ Pulseless Electrical Activity (PEA)
What it is:
The monitor shows a rhythm, but there is no pulse. The heart’s electrical system works, but the muscle can’t pump.
What it looks like on EKG:
- Can look like normal sinus rhythm, bradycardia, or other organized rhythm — but there’s NO PULSE.
What to do:
- Call a Code Blue.
- Start CPR immediately.
- Do NOT shock — you can’t shock PEA.
- Give epinephrine and look for causes:
- H’s: Hypoxia, hypovolemia, hydrogen ion (acidosis), hyper/hypokalemia, hypothermia.
- T’s: Tension pneumothorax, tamponade, toxins, thrombosis (MI, PE).
5️⃣ Torsades de Pointes
What it is:
A special kind of V-Tach with twisting peaks. It’s linked to low magnesium or prolonged QT interval. It can suddenly turn into V-Fib.
What it looks like on EKG:
- Polymorphic V-Tach: QRS complexes twist up and down around the baseline, forming a ribbon or spindle shape.
What to do:
- If unstable, defibrillate!
- Give IV magnesium sulfate.
- Correct low potassium.
- Stop any meds that prolong QT (like certain antibiotics or antiarrhythmics).
🗝️ Quick Rhythm Comparison
| Rhythm | Pulse? | Shockable? | What to Do |
|---|---|---|---|
| V-Tach (pulseless) | ❌ No | ✅ Yes | CPR + defibrillation |
| V-Fib | ❌ No | ✅ Yes | CPR + defibrillation |
| Asystole | ❌ No | ❌ No | CPR + epi + fix causes |
| PEA | ❌ No | ❌ No | CPR + epi + fix causes |
| Torsades | ❌ No or unstable | ✅ Yes | CPR + defib + magnesium |
✅ How to Master These Rhythms
✔️ Check the patient first: The monitor doesn’t tell you if there’s a pulse — you must check!
✔️ Memorize key patterns: Wide QRS = V-Tach, squiggly mess = V-Fib, flat = asystole, normal rhythm with no pulse = PEA.
✔️ Know what to do:
- Shockable? Defibrillate.
- Not shockable? CPR, epi, and fix causes.
✔️ Practice ACLS: Take regular mock codes, practice reading strips, and drill with your team.
❤️ Nurse’s Role in a Code
During a real cardiac arrest, every second counts. Nurses must:
- Call the code immediately.
- Start high-quality CPR.
- Grab the crash cart and attach defibrillator pads.
- Know meds like epi, amiodarone, magnesium.
- Communicate clearly with the code leader.
Confidence comes with practice. Use simulation labs and review strips often.
🎓 Key Takeaways
✅ V-Tach and V-Fib: Defibrillate!
✅ Asystole and PEA: CPR, epi, fix cause — no shock.
✅ Torsades: Magnesium + defib if unstable.
Stay calm, stay focused, and trust your training — you are the patient’s best chance for survival.